Engine speed retardation on transmission upshift

Abstract

An engine control provides rapid decrease in the output speed of the engine when an upshift of the transmission is being actuated. The system selectively actuates a speed retardation system to decrease the engine output speed to match a desired engine output speed at the next highest gear ratio. In one embodiment, an engine control actuates engine braking to achieve this rapid speed reduction. In other embodiments, an additional load may be placed on the engine, such as the actuation of a fan. An operator is preferably provided with a shift intent switch that provides an indication to the engine control that an upshift will be actuated. The engine control waits for an indication that the transmission has been moved to neutral. Once this indication is received, the speed retardation system is actuated to rapidly reduce the engine output speed toward a desired value. Most preferably, this feature is incorporated into an engine control system adapted to synchronize the engine output speed to that desired at the next gear ratio, both when the transmission is being upshifted or downshifted. The engine control system allows an operator to achieve a transmission shift without complicated clutching of the transmission.

The invention claimed is: 
     
       1. A method of operating a vehicle drive comprising the steps of: a) providing an engine having an output shaft, a transmission connected to be driven by said engine output shaft, an engine control for controlling the output speed of said engine output shaft, said engine control having means for identifying when a transmission upshift will occur, and a speed retardation system for rapidly reducing the speed of said engine output shaft, the actuation of said speed retardation system being controlled by said engine control unit;   b) monitoring the operation of said vehicle with said engine control, to predict when a transmission upshift is likely; and   c) actuating said engine speed retardation system when an upshift is being performed to rapidly decrease the output speed of said engine output shaft;   wherein said speed retardation system comprises (i) opening at least one outlet valve of a cylinder of said engine before the initiation of a power stroke of said engine, (ii) selectively connecting a fan to be driven by said engine, (iii) actuating a shunt resistor to drain power from said engine to an alternator connected to said engine.   
     
     
       2. A method as recited in claim 1, wherein said transmission provides a signal to said engine control when said transmission has been moved to neutral, and the actuation of step c) is not performed until said signal that said transmission is in neutral is received by said engine control. 
     
     
       3. A method as recited in claim 1, wherein said engine control predicts a desired engine speed at the next highest speed ratio to achieve a smooth transition to said next highest speed ratio, and said engine control controls actuation of said speed retardation system, and at least one other engine variable to rapidly achieve said desired engine speed. 
     
     
       4. A method as recited in claim 3, wherein said other variable is controlling the amount of fuel being delivered to said engine to achieve said desired engine speed. 
     
     
       5. A method as recited in claim 4, wherein said speed retardation system is an engine braking system for reducing the output of said engine output shaft. 
     
     
       6. A method as recited in claim 4, wherein said speed retardation system includes actuating an additional load of said engine. 
     
     
       7. A method as recited in claim 1, wherein an operator is provided with a shift intent switch that allows the operator to provide a signal of when an upshift is to be actuated, said signal providing the prediction of step b). 
     
     
       8. A method as recited in claim 1, wherein said engine control monitors vehicle conditions to make the prediction of step b). 
     
     
       9. A method as recited in claim 1 wherein said speed retardation system further comprises (iv) transmission braking. 
     
     
       10. A method of operating a vehicle comprising the steps of: a) providing an engine having an output shaft, a multi-speed transmission connected to be driven by said engine output shaft, a speed retardation system to rapidly decrease the output speed of said engine output shaft, an engine control selectively operable to actuate said speed retardation system, and an operator shift intent switch to allow an operator to provide a signal to said engine control of when a transmission upshift is being actuated;   b) sensing an indication of an upshift from said operator switch;   c) predicting a desired engine speed at the next highest gear based upon a sensed transmission output speed and the speed ratio of the next highest gear;   d) providing a signal from said transmission to said engine control once said transmission has been moved out of an engaged gear position to a neutral position; and   e) actuating said speed retardation system to rapidly decrease said engine output speed toward said desired engine speed;   wherein said speed retardation system comprises (i) opening at least one outlet valve of a cylinder of said engine before the initiation of a power stroke of said engine, (ii) selectively connecting a fan to be driven by said engine, (iii) actuating a shunt resistor to drain power from said engine to an alternator connected to said engine.   
     
     
       11. A method as recited in claim 10, wherein said engine control also controls engine speed by varying the fuel delivered to said engine. 
     
     
       12. A method as recited in claim 11, wherein said engine control monitors actual engine speed and compares said actual engine speed to said desired engine speed, said engine control deactivating said speed retardation system as said actual and desired engine speeds approach each other. 
     
     
       13. A method as recited in claim 10, wherein said speed retardation system further comprises (iv) transmission braking. 
     
     
       14. A vehicle drive comprising: an engine having an output shaft;   a multi-speed transmission having an input connected to said engine output shaft, and an output for driving a vehicle;   an engine speed retardation system to be selectively actuated to reduce the output speed on said engine output shaft; and   an engine control, said engine control being operable to sense when an upshift in said multi-speed transmission is being actuated and to actuate said speed retardation system upon initiation of an upshift to reduce the speed of said engine output shaft;   wherein said speed retardation system comprises (i) opening at least one outlet valve of a cylinder of said engine before the initiation of a power stroke of said engine, (ii) selectively connecting a fan to be driven by said engine, (iii) actuating a shunt resistor to drain power from said engine to an alternator connected to said engine.   
     
     
       15. A vehicle drive as recited in claim 14, wherein said engine control is further operable to synchronize said engine speed with a desired engine speed at the next expected speed ratio during a transmission speed shift. 
     
     
       16. A vehicle drive as recited in claim 14, wherein said speed retardation system further comprises (iv) transmission braking. 
     
     
       17. A vehicle drive as recited in claim 14, wherein said engine control receives a signal that said transmission has been moved to a neutral position before said engine control begins actuation of said speed retardation system. 
     
     
       18. A vehicle drive as recited in claim 14, wherein an operator of the vehicle is provided with a shift intent switch to provide an indication to said engine control of when an engine upshift is being initiated, and to actuate said speed retardation system when the upshift is initiated. 
     
     
       19. A vehicle drive as recited in claim 14, wherein said engine unit is operable to predict when an upshift is to be expected, based upon sensed vehicle conditions.